Feeder

[paul renshaw]

I have seen a couple of installations recently that had #2 SER AL run to a sub panel in a residence and protected by a 100 amp breaker. Shouldn't that be on a 90 amp breaker? When I questioned this to an inspector, he told me the exception in Table 310.15 allows this. I read it as to only be for 3-wire feeders and SE conductors that are the main power feeders. Is there something here that I am missing?

 

[infinity]

You are correct under previous code editions. Now that feeder is only good for 75 amps due to SE cable being limited 60? C ampacity.

 

[Little Bill]

I have seen a couple of installations recently that had #2 SER AL run to a sub panel in a residence and protected by a 100 amp breaker. Shouldn't that be on a 90 amp breaker? When I questioned this to an inspector, he told me the exception in Table 310.15 allows this. I read it as to only be for 3-wire feeders and SE conductors that are the main power feeders. Is there something here that I am missing?

Did you mean Table 310.56(B)(6)? If so, then it can only be used if the sub panel supplies the entire load to the building.

 

[paul renshaw]

In a residence if you have a service disconnect at the meter, and SER run from there to the main panelboard in the house, would it fall under 310.15 B 7? It says 3 wire service and feeders, is SER considered 4 wire or 3 wire?

 

[stew]

It says 3 wire services and feeders but you must read the entire paragraph. It also says they must serve the entire load and not just the sub. Inspectors miss this all the time. A lot dont read past the header either.

 

[roger]

In a residence if you have a service disconnect at the meter, and SER run from there to the main panelboard in the house, would it fall under 310.15 B 7? It says 3 wire service and feeders, is SER considered 4 wire or 3 wire?

It wouldn't matter how many conductors are in a cable or raceway, the only thing that matters is the number of conductors being used which would be three (and an EGC) in your scenario.

Roger

 

[paul renshaw]

I didn't think you counted EGC, but have been arguing that all morning, and as long as it is serving the whole load, the table applies. I will be passing this on to the non-believers, Thanks for info.

 

[Twoskinsoneman]

I have seen a couple of installations recently that had #2 SER AL run to a sub panel in a residence and protected by a 100 amp breaker. Shouldn't that be on a 90 amp breaker? When I questioned this to an inspector, he told me the exception in Table 310.15 allows this. I read it as to only be for 3-wire feeders and SE conductors that are the main power feeders. Is there something here that I am missing?

FWIW I agree that you shouldn't be allow to do this per code but around here the inspectors disagree and allow it.
Wanted to add that I spoke to one inspector in my county that explained to me he knew the rule but allows it based on the extremes in pricing, based on the abundant availability of the 2-2-2-4 Al SER cables which seem to be used everywhere for 100A subs.

 

[Dennis Alwon]

In a residence if you have a service disconnect at the meter, and SER run from there to the main panelboard in the house, would it fall under 310.15 B 7? It says 3 wire service and feeders, is SER considered 4 wire or 3 wire?

It should read as 3 wire services, AND feeders. It does not mean 3 wire feeders. Also ser would be consider 4 wire IMO.

 

[infinity]

In a residence if you have a service disconnect at the meter, and SER run from there to the main panelboard in the house, would it fall under 310.15 B 7? It says 3 wire service and feeders, is SER considered 4 wire or 3 wire?

SER is 4 wires but it would still be a 3-wire feeder for the purposes of that table.